The present invention is directed to a system for converting liquid nitrogen to gaseous nitrogen. It is well known to convert liquid nitrogen to gaseous nitrogen which can be used in industrial, petrochemical and oil field industries. For example, it is known, as disclosed in U.S. Pat. No. 4,920,271, to provide a self-contained, flameless nitrogen liquid to gas converter. However, such systems require high horsepower engines, or additional heat engines as in U.S. Pat. No. 4,458,633. These systems operate at a greater level of power than necessary, driving multiple pumps and motors. The prior art systems use loading devices such as hydraulic variable back pressure valves to create a load on the engines. These high horsepower engines consume large amounts of fuel, for converting the fuel consumed to waste heat which is transferred to a number of different heat exchangers which increase the complexity of the system and leads to reduced reliability.